v2.13 Cleverscope CS300 Reference Manual
©Cleverscope 2004-2018 www.cleverscope.com Page 131
Go to the Maths Equation Builder window.
Enter equation (a-b)*714
Click Apply Equations
Return to the Cleverscope Control Panel window.
On the Settings menu, click Analog Names and Units.
In the Maths Graph Units area, change A Units to
mA
and A Name to
Current
.
Click OK.
Note The units and names change immediately on
the graphs and information areas.
The A channel graph is much more useful now we
can read the current directly.
We see the following:
The peak current demand is 2366 mA. (Mark1:Chan
A).
The stabilized current demand is 615 mA.
(Mark1:Chan A).
The increased current demand lasts for about 5 ms.
19.7 Example - Deriving Power [Maths]
The B channel shows the actual voltage going into the unit.. Many battery modules are rated in AHr which is
the design continuous current consumption available for one hour of use.
For example, a 9.6 V (8 cell) NiCad battery pack might be rated at 700 mAHr. This mean that after one hour of
700mA constant current drain the battery terminal voltage will have fallen to 80% of the full charge terminal
voltage and the battery will be nearly empty.
For a switch mode power supply we are more interested in the power consumption because the current will
vary with terminal voltage. Assuming a straight line reduction in battery terminal voltage (i.e. an average of
90% of the fully charged terminal voltage) we can estimate the energy content of the battery in Watt Hr (or
Joules, with constant conversion), and use this to calculate actual battery life.
For the 700mAHr 9.6V battery above, the capacity is:
0.9 x 9.6 x 0.7 = 6 Watt Hour, or
0.9 x 9.6 x 0.7 x 3600 = 21.7 kJoule.
Go to the Maths Equation Builder window.
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